1. Field of the Invention
This invention relates to a strip-like reinforcing laminate usable as a composite material for reinforcement and a pneumatic tire using the same.
2. Related Art Statement
The composite material of this type comprises a matrix and a dispersing member or reinforcing member and includes high polymer fiber reinforced plastics (FRP), fiber reinforced thermoplastics (FRTP), fiber reinforced rubber (FRR) and the like.
In the conventional FRP, the reinforcement of plastic matrix is attempted by dispersing powder, short fibers or the like into the matrix, but it sometimes undesirably causes a difference in rigidity at end portion of the region reinforced with fibers or the like dispersing into the matrix. Also it is difficult to achieve the reinforcement of the matrix by dispersing and embedding these fibers and the like.
On the other hand, rubberized cord fabrics in which cords usually obtained by twisting organic fibers or metal filaments, particularly steel wires are arranged in parallel to each other and covered with a coating rubber are generally used as a reinforcing member for pneumatic tires widely used as a product comprised of high polymer composite material. Particularly, in pneumatic tire comprising a toroidal carcass composed of such rubberized cord fabric extending between at least a pair of bead cores, the crown portion of this carcass is, for example, reinforced with a breaker or belt comprised of plural slant members obtained by obliquely cutting the above rubberized cord fabric and piling the cut fabric pieces one upon the other to cross the cords of these pieces with each other. Since such slant members are not favorable in durability because the modulus of elasticity is different between the cord and the coating rubber and also the cord is apt to move toward the end thereof and hence the stress concentration is caused in the vicinity of both side edge portions of the belt positioning ends of the cords all together. Further, the hoop effect through the slant members is large in the vicinity of the central portion of the belt, but a large tension can not be born near to the side edge of the belt, so that the belt is necessary to have a wider width for ensuring the required peripheral tension. As a result, the moving quantity of cord ends increases as the cord length becomes long, which is unfavorable in durability.
Therefore, a so-called fold structure in which the slant member is folded at its cord end, an additional cord layer containing cords arranged in a tension-acting direction and the like are used, but they are obliged to become disadvantageous in the cost.
In addition, the fold structure solves various problems resulting from stress concentration at the cord end for the present, but there are still problems such as fatigue of the cord at the folded portion of the cord, durability based on the difference in rigidity between cord and rubber. On the other hand, the additional cord layer is low in rigidity perpendicular to the cord, so that when the force is applied to the tire in all directions, it is difficult to totally obtain the required performance.
Moreover, British Pat. No. 815,055 discloses an attempt of piling two reinforcing members each containing wave-like cords one upon the other. In this example, only one cord of a first layer and only one cord of a second layer are crossed and superimposed as a pair, so that such a pair of cords in the first and second layers differ a pair of cords adjacent thereto in the rigidity and consequently the function as the reinforcing member is approximately equal to that in the case of the above additional cord layer.